Such devices and methods are used in packaging machines for packaging groups of articles, packs out of several articles and/or pallets. The groups, packs and/or pallets are wrapped in plastic film or another suitable flat sheet-like material. The film sections wrapped around the groups of articles or packs are welded and/or shrunk under heat. The flat material or sheets of film are generally provided as a continuous material and unrolled from big supply rolls. If the material on the rolls is used up or depleted, the rolls must be replaced. When exchanging the rolls the machine should not be stopped. Therefore in known machines the switching between two material rolls is usually done partially or fully automated. Known packaging modules used in the field of one way packaging usually use automatic modules for the welding of the sheets of film. During the exchange of the material rolls these modules connect the end of a sheet of film of an almost depleted unrolled roll of film with a new full film roll. Even when changing to a different type of film old and new film webs are equally welded together.
Since the rolls are often arranged in a lower machine level, mostly unfavorable ergonomic conditions exist for the handling of film rolls. Setting up and fixing the new beginnings of the sheet of film as well as finding and eliminating errors requires a relatively large manual effort from the person operating the machine. The installation space normally available limits the storage volume for the roll of films. As a result of the existing principle of automatic sheet welding only one film roll can usually be stored in reserve. Due to the limited space the roll diameter is limited to a certain maximum. Depending on machine power and depending on the articles to be packed, a relatively frequent roll change has to be carried out by the person operating the machine.
DE 10 2004 032 528 B3 describes a method for performing a roll exchange in a supply unit. Hereby a sheet-like flat material used in a packaging machine is unwound from a roll. A roll exchange is required as soon as the roll is depleted. Hereby the end of the material sheet from the first roll is connected to the beginning of the material sheet of a new full roll by a connecting station. The connecting portion of the material sheet of the new roll is mounted in a holding- and positioning unit for exact positioning. The holding- and positioning unit is associated with the connecting station but located apart from the supply of new full rolls.
DE 10 2006 037 189 A1 discloses a method that is an improvement of the older method described above. Hereby each connecting portion of the material sheet of the new roll is fixed to a positioning element of the connecting station for exact positioning. A corresponding holding and positioning element is formed by a pinch roller that comprises a manually rotatable axis.
EP 0 749 924 A1 discloses a method and apparatus for welding of two sheets of film in a packaging machine, whereby each sheet of film comes from a supply roll. The beginning of the sheet of film belonging to the initially stationary full second supply roll, is deflected and held against the direction of movement of the sheet of film coming from the emptying first supply roll. The status of unrolling the running sheet of film is electronically monitored and a stop signal for the film feeding mechanism is produced, leading to a subsequent compression and welding of the two sheets of film over their entire width. The two sheets of film are arranged anti-parallel to each other. Simultaneously excess end pieces of the sheets of film are separated and a further signal is generated to restart the film feeding mechanism.
From EP 1 600 412 A1 a film splicing station is known that comprises a first and a second roll-off device for one roll of film each. The station comprises a splicing device for splicing the films from the first and second roll-off device at a splicing position, a movable transfer device for transferring a film from a roll-off device to the splicing station and a holding device for stationary holding the film, which can be transferred through the transfer device.